This invention relates to electro-optical detectors, and especially such electro-optical detectors which detect fluids, these fluids being either opaque, translucent or transparent.
Electro-optical detectors in the past have operated on the principal of detecting a loss of signal from a photo-activated, electrical device (pick-up) which device receives a "light" signal from a light source. An object to be detected interrupts or intercepts a beam of light passing between the light source and pick-up electrical device thereby triggering a loss of signal in the pick-up circuit.
While in early years "electric-eye" type devices were used, in recent years light emitting diodes (LED's) and photo transistors have been incorporated into these devices. Such LED/photo transistor circuits are now made much smaller in size, using much less electrical power, and being commercially available at less cost than their predecessor devices.
Regardless of the type of photo electric source/pickup, i.e. LED/photo transistor or otherwise, problems still remain with existing circuits when used for detecting gas or air bubbles in translucent or transparent, fluids. This has been because light transmission through clear fluids has not been easily distinguishable from light transmission through gas or air, i.e. an empty tube. Further, in such applications the change in signal levels between these prior LED/photo transistor detector circuits have, however, operated satisfactorily with opaque objects. Some applications have been as slot detectors where the LED and photo transistor are spaced approximately 1/4 to 1/2 inch apart with a slotted opaque disk passing therethrough.
These prior LED/photo transistor detector circuits have also satisfactorily operated as drop detectors. However, when used as a drop detector, the circuitry has critically depended upon the leading or trailing edge of a fluid drop or gas bubble to bend or distort the light beam, thereby allowing a detection.
Other light source-detector combinations have also been operated as fluid presence detectors, whereof the presence of a fluid causes a reduction in light transmission between the source and detector. Such circuits, such as spectrophotometers often utilize specific absorption frequencies or quantum effects to determine the presence or absence of materials.
Recent application of LED-phototransistor combinations have not been successful in static or in very slow moving fluidic-gas systems.
These prior electro-optical detector devices have universally operated on the physical assumption that light transmission is diminished when passing through a fluid, whether that fluid is clear or translucent, as opposed to passing through air; and blocked entirely by an opaque object or opaque fluid.
By-in-large the electrical and/or electronic circuitry involved with these prior electro-optical detector circuits has been relatively substantial and has involved operating the light source at higher power outputs or specific quantized frequencies for detection; or as in the case of the drop detectors, has required a movement for a detection.
An object of the present invention is to provide a more simple and lower cost light source, electro-optical detector circuit.
A second object is to provide such a detector circuit which does not require movement for a detection.
A further object to provide a detector circuit capable of operating satisfactorily with a variety of fluids from clear fluids, such as water and saline, to colored or dye containing fluids, to reasonably poor translucent fluids such as motor oil or paint pigment.